For example, as described in Patent Literature 1, in such as a pickup truck having a bed at a rear portion of the vehicle body, on a side surface of the vehicle body, a front door pivotally mounted by a hinge at a front end side and a rear door pivotally mounted by a hinge at a rear end side are often provided so that they can be opened and closed in a double hinged manner. In a vehicle having such the door opened and closed in a double hinged manner, it is common that the rear door is closed and is locked to the vehicle body, and then the front door is closed and can be locked to the rear door. On upper and lower portions of a front portion of the rear door, an upper door latch device (an upper latch unit) and a lower door latch device (a lower latch unit) that lock the rear door in a closed state by engaging with a striker provided on a roof side and a lower side portion of the vehicle body are provided respectively.
In addition, as described in Patent Literature 2, for example, an upper door latch device (an upper lock unit) that engages with a striker provided at a side end of a roof side of a vehicle body is provided on an upper portion of a front side door.
Moreover, a conventional upper door latch device comprises a pair of front and rear base members, a latch pivotally mounted on a latch shaft fixed by caulking to both base members and engageable with a striker provided on a roof side of a vehicle body, and a ratchet pivotally mounted on a ratchet shaft fixed by caulking to the front and rear base members and engageable with the latch, wherein the front and rear base members are fixed to an upper portion of an inner panel of the door.